The work proposed for the coming year involves investigation of the shortloop feedback of prolactin, both on its own secretion and that of luteinizing hormone (LH). Measurement of hypothalamic levels of tyrosine hydroxylase and dopamine-beta-hydroxylase will be made as an indication of catecholaminergic activity. This will then be correlated with plasma levels of prolactin and LH. We also intend to investigate the role serotonin has in regulation of prolactin during lactation.